Partitioning

I have a user that wants to partition a table using range partitioning
on a table with currently 70 million rows. In the future the table will
hit about 400 million rows.

However, I checked how much space the table was taking up and saw that
it was only taking up about 100 MB. I haven't normally partitioned tables
under 2GB and wondered if there would be such a large performance gain
to partitioning since the row count is so high that I should partition
anyway.

Any info on this would be great. I'll be testing this later and sure I will
find some things better about partitioning the table even though it is so
small.